I. Field
The following description relates generally to wireless communications and, more particularly, to hierarchical modulation of multiple communication channels simultaneously conveyed through a single carrier.
II. Background
Wireless communication systems have become a nearly ubiquitous means for communication of both voice and data, e.g., video and audio streams, file transfers, web-browsing, and so on. Emergence of new markets for wireless communication, increased complexity of subscriber needs, and competition among network operators have driven substantial development of wireless technologies at the user equipment and network level. Such development has synergistically benefited from a steady development of computing capabilities, or processing power, and miniaturization of computing units.
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power, which typically are finite, regulated and costly resources). Examples of such multiple-access systems include code division multiple access (CDMA) systems; time division multiple access (TDMA) systems; frequency division multiple access (FDMA) systems and orthogonal frequency division multiple access (OFDMA) systems; and space division multiple access (SDMA). Third generation systems like 3rd Generation Partnership Project 2 Ultra Mobile Broadband (UMB) and 3rd Generation Partnership Project Long Term Evolution (LTE) systems exploit one or more of the such multiple-access paradigms.
In advanced wireless architectures, multiple access paradigms have benefited from multiple-input multiple-output mode of communication, which effect telecommunication via multiple transceivers in either a serving access terminal or a receiver, or both devices. In addition, multiplexing of traffic and signal generally relies on Frequency Division Multiplexing (FDM) which is specified differently in downlink than in uplink; while DL utilizes multiple carriers for communication, uplink employs a single carrier (SC) or single-carrier waveform. SC-FDMA provides substantially all advantages on FDM while mitigating peak-to-average ratio (PAPR) fluctuations. Such solution arises at the expense of a somewhat more complex and multiplexing for UL transport and signaling channels: Channels are to be multiplexed in contiguous tones or equally interleaved tones systems exploit single-carrier waveform transport traffic and control. Furthermore, under specific circumstances two channels are required to be transmitted to retain a communication, e.g., a voice or data session, while preserving a subscriber perceived quality of service, to ensure communication is indeed preserved in such instances, various approaches to UL transmission have utilized like joint coding, time-division multiplexing of information, individual coding with multiple Zadoff-Chu sequences. Yet those approaches appear to provide far from complete, effective solutions to the problem of simultaneous multiple channel transmission.
Therefore there is a need for a transmission formalism for communication of multiple communication channels with SC-FDMA waveform.